<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>this相关</title>
  </head>
  <body>
    <button>提交</button>
    <script>
      let btn = document.querySelector('button')
      function handle() {
        console.log(this)
      }
      btn.addEventListener('click', function callback() {
        console.log(this)
        handle.apply(this)
      })
    </script>
  </body>
</html>
